The present invention concerns a process and an apparatus for encapsulating microbial, vegetable and animal cells or biological and chemical substances through a nozzle into small, substantially spherical particles.
The encapsulation of microbial, vegetable and animal cells and biological and chemical substances such as catalysts is a matter of great significance in particular in biotechnology and medicine for immobilization purposes. In medicine encapsulation additionally serves to provide shielding from the immune system. By virtue of the immobilization effect, it is possible to retain the cells or the catalyst in the process and at the same time harvest the product. That makes it possible to achieve prolonged utility and an enhanced level of space-time yield. By virtue of the shielding effect for the cells from the immune system, it is possible to implant in a patient cells that are foreign to the patient's body and which over a prolonged period of time discharge a desired substance into the body of the patient without their being attacked and destroyed by the immune system of the patient.
The encapsulation of cells and catalysts in biopolymers such as carrageenan or alginate and synthetic polymers such as polyacrylamide is a method which has been used for some years in research laboratories. Many different apparatuses are described for that purpose in the literature. One of the most efficient methods involves dividing up a jet by the superimposition of an external oscillation or vibration on the immobilization fluid. That procedure provides that, as it is discharged from a nozzle in a laminar flow, the fluid is divided up into equal-sized fractions. A number of methods for vibration transmission are used or described, for example coupling to a vibrator, piezoelectric crystal, sound waves.
The applicants' WO 96/28247 shows a commercial encapsulation apparatus in which the vibration is transmitted by a rigid connection to a vibrator. That method suffers from the difficulty that the axis of the vibrator and the axis of the nozzle must be precisely aligned as otherwise disturbance phenomena occur, which have a massively adverse effect on the homogeneity of the sphere size. In addition the vibrator is expensive.
In consideration of that state of the art, the inventor set himself the aim of optimising an apparatus and a process of the kind set forth above.